Activity in a modified open-field apparatus: effect of diazepam and prenatal stress

We examined the effect of prenatal stress exposure on sensitivity to diazepam. The stress exposure consisted of handling pregnant rats 5 minutes daily from the 14th to 21st day of gestation. Male offspring were tested at 60 days of age in a modified open-field apparatus 30 minutes after injection with diazepam (0, 1, 5 mg/kg). The 5 mg/kg dose of diazepam depressed the frequency and duration of crossover, rearing, headpoke and corner activities. Rearing was not affected by the 1 mg/kg dose of diazepam. Defecation was increased by the 1 mg/kg dose, but was decreased by 5 mg/kg of diazepam. Prenatal stress exposure altered responsiveness to diazepam on only crossover activity and on defecation. Prenatally stressed animals exhibited an increase in crossover at the low dose of diazepam, while control offspring were insensitive to this dose level. Also, there were more boli in prenatally stressed rats treated with 1 mg/kg diazepam, while the 5 mg/kg dose of the drug decreased the number of boli. The other measures showed a trend in the same direction but the differences were not statistically significant. Thus our results indicate that prenatal stress has very specific effects on the sensitivity of adult offspring to diazepam.